/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package us.ihmc.ros2;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * A class that performs some subnet calculations given a network address and a subnet mask.
 * @see "http://www.faqs.org/rfcs/rfc1519.html"
 * @author <rwinston@apache.org>
 * @since 2.0
 */
class SubnetUtils {

   private static final String IP_ADDRESS = "(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})";
   private static final String SLASH_FORMAT = IP_ADDRESS + "/(\\d{1,3})";
   private static final Pattern addressPattern = Pattern.compile(IP_ADDRESS);
   private static final Pattern cidrPattern = Pattern.compile(SLASH_FORMAT);
   private static final int NBITS = 32;

   private int netmask = 0;
   private int address = 0;
   private int network = 0;
   private int broadcast = 0;

   /** Whether the broadcast/network address are included in host count */
   private boolean inclusiveHostCount = false;


   /**
    * Constructor that takes a CIDR-notation string, e.g. "192.168.0.1/16"
    * @param cidrNotation A CIDR-notation string, e.g. "192.168.0.1/16"
    * @throws IllegalArgumentException if the parameter is invalid,
    * i.e. does not match n.n.n.n/m where n=1-3 decimal digits, m = 1-3 decimal digits in range 1-32
    */
   SubnetUtils(String cidrNotation) {
      calculate(cidrNotation);
   }

   /**
    * Constructor that takes a dotted decimal address and a dotted decimal mask.
    * @param address An IP address, e.g. "192.168.0.1"
    * @param mask A dotted decimal netmask e.g. "255.255.0.0"
    * @throws IllegalArgumentException if the address or mask is invalid,
    * i.e. does not match n.n.n.n where n=1-3 decimal digits and the mask is not all zeros
    */
   SubnetUtils(String address, String mask) {
      calculate(toCidrNotation(address, mask));
   }


   /**
    * Returns <code>true</code> if the return value of {@link SubnetInfo#getAddressCount()}
    * includes the network address and broadcast addresses.
    * @since 2.2
    */
   public boolean isInclusiveHostCount() {
      return inclusiveHostCount;
   }

   /**
    * Set to <code>true</code> if you want the return value of {@link SubnetInfo#getAddressCount()}
    * to include the network and broadcast addresses.
    * @param inclusiveHostCount
    * @since 2.2
    */
   public void setInclusiveHostCount(boolean inclusiveHostCount) {
      this.inclusiveHostCount = inclusiveHostCount;
   }



   /**
    * Convenience container for subnet summary information.
    *
    */
   public final class SubnetInfo {
      private SubnetInfo() {}

      private int netmask()       { return netmask; }
      private int network()       { return network; }
      private int address()       { return address; }
      private int broadcast()     { return broadcast; }

      private int low() {
         return (isInclusiveHostCount() ? network() :
               broadcast() - network() > 1 ? network() + 1 : 0);
      }

      private int high() {
         return (isInclusiveHostCount() ? broadcast() :
               broadcast() - network() > 1 ? broadcast() -1  : 0);
      }

      /**
       * Returns true if the parameter <code>address</code> is in the
       * range of usable endpoint addresses for this subnet. This excludes the
       * network and broadcast adresses.
       * @param address A dot-delimited IPv4 address, e.g. "192.168.0.1"
       * @return True if in range, false otherwise
       */
      public boolean isInRange(String address) {
         return isInRange(toInteger(address));
      }

      private boolean isInRange(int address) {
         int diff = address - low();
         return (diff >= 0 && (diff <= (high() - low())));
      }

      public String getBroadcastAddress() {
         return format(toArray(broadcast()));
      }

      public String getNetworkAddress() {
         return format(toArray(network()));
      }

      public String getNetmask() {
         return format(toArray(netmask()));
      }

      public String getAddress() {
         return format(toArray(address()));
      }

      /**
       * Return the low address as a dotted IP address.
       * Will be zero for CIDR/31 and CIDR/32 if the inclusive flag is false.
       *
       * @return the IP address in dotted format, may be "0.0.0.0" if there is no valid address
       */
      public String getLowAddress() {
         return format(toArray(low()));
      }

      /**
       * Return the high address as a dotted IP address.
       * Will be zero for CIDR/31 and CIDR/32 if the inclusive flag is false.
       *
       * @return the IP address in dotted format, may be "0.0.0.0" if there is no valid address
       */
      public String getHighAddress() {
         return format(toArray(high()));
      }

      /**
       * Get the count of available addresses.
       * Will be zero for CIDR/31 and CIDR/32 if the inclusive flag is false.
       * @return the count of addresses, may be zero.
       */
      public int getAddressCount()                {
         int count = broadcast() - network() + (isInclusiveHostCount() ? 1 : -1);
         return count < 0 ? 0 : count;
      }

      public int asInteger(String address) {
         return toInteger(address);
      }

      public String getCidrSignature() {
         return toCidrNotation(
               format(toArray(address())),
               format(toArray(netmask()))
         );
      }

      public String[] getAllAddresses() {
         int ct = getAddressCount();
         String[] addresses = new String[ct];
         if (ct == 0) {
            return addresses;
         }
         for (int add = low(), j=0; add <= high(); ++add, ++j) {
            addresses[j] = format(toArray(add));
         }
         return addresses;
      }

      /**
       * {@inheritDoc}
       * @since 2.2
       */
      @Override
      public String toString() {
         final StringBuilder buf = new StringBuilder();
         buf.append("CIDR Signature:\t[").append(getCidrSignature()).append("]")
            .append(" Netmask: [").append(getNetmask()).append("]\n")
            .append("Network:\t[").append(getNetworkAddress()).append("]\n")
            .append("Broadcast:\t[").append(getBroadcastAddress()).append("]\n")
            .append("First Address:\t[").append(getLowAddress()).append("]\n")
            .append("Last Address:\t[").append(getHighAddress()).append("]\n")
            .append("# Addresses:\t[").append(getAddressCount()).append("]\n");
         return buf.toString();
      }
   }

   /**
    * Return a {@link SubnetInfo} instance that contains subnet-specific statistics
    * @return new instance
    */
   public final SubnetInfo getInfo() { return new SubnetInfo(); }

   /*
    * Initialize the internal fields from the supplied CIDR mask
    */
   private void calculate(String mask) {
      Matcher matcher = cidrPattern.matcher(mask);

      if (matcher.matches()) {
         address = matchAddress(matcher);

         /* Create a binary netmask from the number of bits specification /x */
         int cidrPart = rangeCheck(Integer.parseInt(matcher.group(5)), 0, NBITS);
         for (int j = 0; j < cidrPart; ++j) {
            netmask |= (1 << 31-j);
         }

         /* Calculate base network address */
         network = (address & netmask);

         /* Calculate broadcast address */
         broadcast = network | ~(netmask);
      } else {
         throw new IllegalArgumentException("Could not parse [" + mask + "]");
      }
   }

   /*
    * Convert a dotted decimal format address to a packed integer format
    */
   private int toInteger(String address) {
      Matcher matcher = addressPattern.matcher(address);
      if (matcher.matches()) {
         return matchAddress(matcher);
      } else {
         throw new IllegalArgumentException("Could not parse [" + address + "]");
      }
   }

   /*
    * Convenience method to extract the components of a dotted decimal address and
    * pack into an integer using a regex match
    */
   private int matchAddress(Matcher matcher) {
      int addr = 0;
      for (int i = 1; i <= 4; ++i) {
         int n = (rangeCheck(Integer.parseInt(matcher.group(i)), -1, 255));
         addr |= ((n & 0xff) << 8*(4-i));
      }
      return addr;
   }

   /*
    * Convert a packed integer address into a 4-element array
    */
   private int[] toArray(int val) {
      int ret[] = new int[4];
      for (int j = 3; j >= 0; --j) {
         ret[j] |= ((val >>> 8*(3-j)) & (0xff));
      }
      return ret;
   }

   /*
    * Convert a 4-element array into dotted decimal format
    */
   private String format(int[] octets) {
      StringBuilder str = new StringBuilder();
      for (int i =0; i < octets.length; ++i){
         str.append(octets[i]);
         if (i != octets.length - 1) {
            str.append(".");
         }
      }
      return str.toString();
   }

   /*
    * Convenience function to check integer boundaries.
    * Checks if a value x is in the range (begin,end].
    * Returns x if it is in range, throws an exception otherwise.
    */
   private int rangeCheck(int value, int begin, int end) {
      if (value > begin && value <= end) { // (begin,end]
         return value;
      }

      throw new IllegalArgumentException("Value [" + value + "] not in range ("+begin+","+end+"]");
   }

   /*
    * Count the number of 1-bits in a 32-bit integer using a divide-and-conquer strategy
    * see Hacker's Delight section 5.1
    */
   int pop(int x) {
      x = x - ((x >>> 1) & 0x55555555);
      x = (x & 0x33333333) + ((x >>> 2) & 0x33333333);
      x = (x + (x >>> 4)) & 0x0F0F0F0F;
      x = x + (x >>> 8);
      x = x + (x >>> 16);
      return x & 0x0000003F;
   }

   /* Convert two dotted decimal addresses to a single xxx.xxx.xxx.xxx/yy format
    * by counting the 1-bit population in the mask address. (It may be better to count
    * NBITS-#trailing zeroes for this case)
    */
   private String toCidrNotation(String addr, String mask) {
      return addr + "/" + pop(toInteger(mask));
   }
}